Regular Expressions 101

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/
\bAmazon\b(?!(?:(?!<\/?a\b[^>]*>).)*?<\/a>)
/
gm
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Amazon
matches the characters Amazon literally (case sensitive)
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Negative Lookahead
(?!(?:(?!<\/?a\b[^>]*>).)*?<\/a>)
Assert that the Regex below does not match
Non-capturing group
(?:(?!<\/?a\b[^>]*>).)*?
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
Negative Lookahead
(?!<\/?a\b[^>]*>)
Assert that the Regex below does not match
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
\/
matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
a matches the character a with index 9710 (6116 or 1418) literally (case sensitive)
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Match a single character not present in the list below
[^>]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
> matches the character > with index 6210 (3E16 or 768) literally (case sensitive)
> matches the character > with index 6210 (3E16 or 768) literally (case sensitive)
. matches any character (except for line terminators)
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
a>
matches the characters a> literally (case sensitive)
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String